A walk-behind working machine has a machine body and a wheel mounted on the machine body for undergoing rotation to move the walk-behind working machine along a ground surface. A cultivator device is mounted on the machine body for cultivating the ground. A working device attachment is removably connected to the machine body for working the ground. A connection mechanism removably connects the working device attachment to the machine body. The connection mechanism has a pair of link members each pivotally connected at a first end portion thereof to the working device attachment and a control unit for controlling a position of the working device attachment with respect to the ground surface so that when the working operation, the first end portions of the link members are disposed closer to the ground surface than the second end portions of the link members.